[Blood of Tyrants]

I would think the high winding rotary engine would need to be geared down for a propeller.

[Ozark Tom]

The LiquidPiston™ engine can be considered as a Wankel turned inside-out then greatly improved. Much lighter for the output and easily double/treble the efficiency. Will debut in the UAV market as well as a range extender application.

https://www.sae.org/news/2018/03/x-marks-the-spot

https://www.armyrecognition.com/august_2018_global_defense_security_army_news_industry/usa_liquidpiston_presents_small_compression_ignited_rotary_engine_at_gvsets.html

https://www.prweb.com/releases/liquidpiston_to_showcase_next_generation_rotary_engine_at_the_turbine_engine_technology_symposium/prweb15749457.htm